Make stream event dataclasses not keyword-only

Since all attributes have different types, it is not too error prone
to allow using positional arguments, and this makes the dataclass
automatically provides a `__match__` dunder method that allows for less
verbose match syntax.

We also update examples to use the match syntax to extra the event
information more easily.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

RELEASE_NOTES.md

@@ -19,8 +19,8 @@
         match msg:
             case StreamStarted():
                 print("Stream started")
-            case StreamStopped() as event:
-                print(f"Stream stopped, reason {event.exception}, retry in {event.retry_time}")
+            case StreamStopped(delay, error):
+                print(f"Stream stopped, reason {error}, retry in {delay}")
             case int() as output:
                 print(f"Received message: {output}")
     ```

src/frequenz/client/base/streaming.py

@@ -26,12 +26,12 @@
 """The output type of the stream."""
 
 
-@dataclass(frozen=True, kw_only=True)
+@dataclass(frozen=True)
 class StreamStarted:
     """Event indicating that the stream has started."""
 
 
-@dataclass(frozen=True, kw_only=True)
+@dataclass(frozen=True)
 class StreamStopped:
     """Event indicating that the stream has stopped."""
 
@@ -81,8 +81,8 @@ def async_range() -> AsyncIterable[int]:
             match msg:
                 case StreamStarted():
                     print("Stream started")
-                case StreamStopped() as event:
-                    print(f"Stream stopped, reason {event.exception}, retry in {event.retry_time}")
+                case StreamStopped(delay, error):
+                    print(f"Stream stopped, reason {error}, retry in {delay}")
                 case int() as output:
                     print(f"Received message: {output}")
         ```